Both humans and cylons take the road to the darkness. Battlestar Galactica was always a dark series, this episode is the epitome of this darkness.
The nemesis is coming for Cylons. There hubris was their desire to become beings above their makers. And as series go, they are starting more and more to become what they hate.
Cylons broke their unity. Cylons started lying to each other. Cylons start murdering each other. They start becoming what they despise and hate. Oh, the irony of it...
And humans? Confused, untrusting, paranoid... Roslin becomes obsessive and starts to develop messianic syndroms. I wonder, is she the dying leader the scriptures have foreseen?